To examine the impact of enforcement of age-restricted tobacco sales on adolescent tobacco purchasing and smoking, we compared the Central Coast intervention area to the rest of New South Wales (NSW) and Australia. We collected data on students in school years 7-12 from triennial health surveys at baseline in 1993 through 2002. Attempts by minors to purchase tobacco in the intervention area declined by 73.6 per cent between 1993 and 2002. Between 1993 and 1996 the prevalence of smoking declined in the Central Coast intervention area, while remaining unchanged in NSW as a whole and nationally (P<0.0001). Between 1993 and 2002, the prevalence of current smoking in the intervention area was reduced by half. Effective enforcement of an age-restricted tobacco sales law was accompanied by a substantial reduction in attempted purchases of tobacco and of smoking by youth. The long-term follow-up in this study allows us to observe that the impact of the intervention was not only sustained but also increased with time.